K-H.Baumann, C. Sprengel: Morphological variations of coccolith species ... , p. 185-193.

Journal of Nannoplankton Research, 22, 3, 2000.

MORPHOLOGICAL VARIATIONS OF SELECTED COCCOLITH
SPECIES IN A SEDIMENT TRAP NORTH OF THE CANARYISLANDS
Karl-Heinz Baumann* & Claudia Sprengel
FE Geowissenschaften, Universittit Bremen, Postfach 330440, 28334 Bremen, Germany;*khb@mail.sedpal.uni-bremen.de

Abstract: Biometrical analyses were performed on nearly 3 200 specimens of distinct coccolith species
from the time-series station ESTOC (E uropean Station for Time-series in the Ocean, Canary Islands).
Originally begun for calcu lation of modern species-specific carbon ate fluxes , this study was further
intensifi ed, both to improve our knowledge of the morphologi cal variability for each of the investi gatedspecies, and to check th e seasonal size-variations of the various species . Besides the dominant t axa
Emiliania hux leyi and Florisphaera profunda, intensive measurements of various parameters have been
made on Calcidiscus leptoporus, Gephyrocapsa spp., Helicosp ha era carteri, Syracosphaera pulchra, andUmbilicosphaera sibogae. Generally, the spec ies are unimoda ll y di stributed , with respect to length/
diameter, and show only slight seasonal variation.

Introduction
Changes in the morphology of
microfossil hard parts, as the basis
for taxonomic identification, are mo~t
commonly used for reconstructionsof evolutionary patterns andprocesses , especially withincoccolithophores (e.g. Samtleben,
1980 ; Young, 1990 ; Wei , 1992 ;Baumann, 1995;Kameo & Takayama,
1999 ; Knappertsbusch, 2000) .
However, for the interpretation ofevolutionary development, it isimportant to know the present
morphological variability as well as
the biogeographical distribution of
the species. At present, this has been
worked out only for very few,
abundant coccolithophore species/
genera, such as Emiliania huxleyi(Young & Westbroek , 1991) ,Gephyrocapsa spp. (Bollmann, 1997)
and Calcidiscus leptoporus(Knappertsbusch et al. , 1997).

w

16°

20°

Madeira

go

120

_.
~.
ESTOC Cl6m {1000m)

32°( a ) ~t '0~; -~
7s .d

(b )

£. huxlt)'l

28°
Canarylslan~s~~'")I/

24° ~----------------~------~

0

G tricSOIIII0•

G mut:lluat
G ('IU(lniCD0

F proju11do0

C. ltptoponu
U. Slbogot•m

DJ FMAMJ

JA

0

S. pulchra

0

0

1996

Figure 1: Location of th e sedim ent trap mooring ESTOC (CI6m) and main surface-water
currents (AC - Azores Current, CC - Canary Current). Additional data on the right-hand sidein clud e (a) monthl y mean sea-surface temperature (SST) for th e se diment trap mooring
location (29. 1°N, 15 .5°W) for the peri od November 1995 to December 1996, and (b) the
cocco lith flu x data (not to scale! ) of th e investigated species (from Sprengel et al., 2000).

Changes in morphology through time do not necessarily
indicate evolution. Size can be controlled genotypically, as
has been shown to be important within E. huxleyi, but may
also reflect ecological conditions within other species(Young & Westbroek , 1991 ; Baumann, 1995 ;Knappertsbusch et al., 1997). The overall morphology ofmany species often varies with size, and strong size
variation is evident in both living and fossil samples (Young& Westbroek, 1991). Study of size variation in living oceanic
coccolithophore species is therefore a prerequisite, bothin improving our knowledge of the morphological range ofthe species, and in applying this knowledge topalaeontological and palaeoceanographical studies.
In the present study, samples from a year-round mooredsediment trap (CI6m) at 1 OOOm water-depth, from 60 nautical
miles north of Gran Canaria (Figure 1) were investigated inorder to measure the morphological variation of selectedcoccolith species. This study was originally undertaken
to provide a more exact determination of modem speciesspecific carbonatefluxes (Sprengel et al., 2000), by using
mean-length data of various species in a formula given by
Young & Ziveri (2000). Besides providing information on
the seasonal succession of species, sediment trapping also
gives the opportunity to study seasonal variation in themorphology of coccoliths. Therefore, this aspect has beenmuch intensified in the latter part of the work.
The mooring is located in the Eastern Booodary Current
regime of the subtropical North Atlantic gyre. This is atransition zone between relatively nutrient-rich waters
along the North African continent to the east and moreoligotrophic waters of the North Atlantic gyre to the west
and, thus, seems to be well-suited to address the abovementioned problems. The monthly averaged sea-surface

185

K-HBaumann, C. Sprengel: Morphological variations of coccolith species... , p. 185-193.

Journal of Nannoplankfon Research, 22, 3, 2000.

temperatures (SSTs) for 1996
show a 'normal' North
Atlantic seasonality, withminimum SSTs (18 .6°C) in
February and March, andmaximum SSTs (up to 23.5° C)
in September (Figure 1).
Maximum coccolith fluxes
recorded at ESTOC are
closely related to the periodof lowest SSTs and highest
pigment concentration(Sprengel et al., 2000).
Highestfluxes of>4500x106
coccoliths m-2d- 1 wereobserved in late winter/early
spring, whereas lowest
values of <20x 106 coccoliths
m- 2 d- 1 generally occurred
during summer months(Sprengel et al., 2000; Figure1). Emiliania huxleyi ,Calcidiscus leptoporus
2

4

10

8

6

Diam te•·

12

40
>.
u

c:

Cl)

;::>

0'

30

td th of

20

Cl)

'-

U,

Di . tal hieldelement

10
0
40
0

1-

V>

c
Cl)

0

:

E 30 Cl)

U3
"0

i.;r·
0

'

20 -

0

z

0
0

0

:0

8 ,.. 0,~·'

E

....

3

Cl)

@
~

....

0
0

c:

:

0

:

Cl)

u

0

10
6
Di ameter (!lm)

2-

~

0

0

4

:

0

0 :

0
0

~.o-~·~-· :102,....,'=0.677 :

12

2

4

T

I

-T

6

8

10

12

Diameter (!lm)

Figure 2: Scatter plots and frequency distribution (of the coccolith diameter, at 0.25f!in intervals)of all C. leptoporu s coccoliths measured. Measured parameters are indicated in the SEM picture.

Florisphaera profunda and Gephyrocapsa ericsonii
dominated the coccolithophore assemblages, whereas allother species generally contributed <10% to thecommunity. Variation in the relative species composition
was low, reflecting similar seasonal flux patterns of thedifferent species during the entire sampling period.
Besides the most abundant species, E. huxleyi and F
profunda, we have selected Gephyrocapsa spp.,

Calcidiscus leptoporus , Umbi licosphaera sibogae,
Helicosphaera carteri and Syracosphaera pulchra,displaying an overview of styles ofthe main morphologicalvariations of coccoliths. Basic aims of this study are: (1) tomeasure (and numerically classify) the morphologicalvariability for each of the investigated species; and (2) tocheck the seasonal distribution of the morphologicalvarieties. This study was conducted in conjunction with
the EU-funded TMR-project, CODENET, which, among
other tasks, aims to study coccolith morphology anddetermine ecophenotypic and genotypic variability of
selected species:

Materials and Methods
For this study, 16 of the 20 samples from the time-series
sediment trap, CI6m, were chosen, all of which had alreadybeen counted for coccolith content (Spreilgel et al. , 2000).
The individual sampling intervals of the mooring is about
three weeks. For coccolithophore analysis, aliquots of eachsample were wet-split by means of an electtical rotarysample divider (Fritsch, Laborette 27) using tap-water as
the split medium . The samples were filtered onto
polycarbonate membrane filters (Schleicher & Schuell
4 7mm diamet~r, 0.45 J.U11 pore-size) using a vacuum pump.
Thereby a monolayer of all sediment particles was created
which was than investigated under the scanning electron
microscope (SEM) (for more details see Sprengel et al.,2000).
Measurements were made using a Zeiss DMS 940A
SEM. For all species, distal shield length and width, or the™

diameter of the distal shield, of about 30 to 50 randomly
chosen specimens were measured. In addition, various
other parameters were measured or counted, such as thesize of the central area (C. leptoporus, E. huxleyi,
Gephyrocapsa spp. and U. sibogae) and the number of
distal shield elements (C. leptoporus, E. huxleyi and U.
sibogae ). All measurements were made directly on the TVscreen at a magnification of 5 OOOx or 10 OOOx by using aninternal Zeiss measuring system. This leads to a resolutionof about 0.1-0.2J.U11. An attempt was made to measurecoccoliths in different areas of the SEM-mounts by movingfrom one measured specimen to the next unmeasured
specimen.

Results and Discussion
Variability of the species:
Coccospheres of Calcidiscus leptoporus (Murray &Blackman, 1898) Loeblich & Tappan, 1978 consist of tightlyinterlocked coccoliths. These placoliths are mostly circularor slightly elliptical in plan-view, with the distal shields
displaying dextrally-imbricated and sigmoidally-shaped
sutures. C. lep toporus was thought to have aholococcolith stage (C. leptoporus f. rigidus) in its lifecycle (Kleijne, 1991 ; Cortes, 2000). However, Geisen et al.
(2000) recently found combination coccospheres of C.
leptoporus together with Syracolithus quadriperforatus
and tentatively explained the combination of two
holococcoliths associated with one heterococcolithophoridby cryptic speciation in the group.
The morphology of a total of 328 individual placoliths
ofthe heterococcolith-bearing stage of the C. leptoporus
group fell into three indistinct clusters of <5 .0J.U11, 5.0 to~8.5Jlm, and >8.5J.U11 (Figure 2). Overall, the diameters ofthe distal shield range from 3. 9 J.U11 to 11.5 J.U11 and the numberof elements from 15 to 34 (Table 1). However, the majorityof measurements are between 6.0Jlm to 8.0J.U11 and 18 to 28
distal shield elements. In addition, a strong correlation (r2= 0.677) of the coccolith diameter and the number of186

K-H.Baumann, C. Sprengel: Morphological variations of coccolith species... , p. 185-193.

CountsMinimum

Maxi mum(in ~m/in °)'(in14m/in °)(in 14mfin •) (in14mfin °)Di ameter
No. of elements
Pore width

328
!59

3.97
15
0.08

11.55
34

Leng thWidth
No. of elements
Po re len gth

803
5 !6

4.43
3.56

3.33

0.33

2.78

51 6

2.38
2.0 1
22
0.79

40
2.07

31
1.4

0.29
3 .56
0.2 1

F. profunda

Length
Width

497
393

1.59
0.94

5.95
3.99

2.78
1.83

0.76
0.48

G. ericsonii

Lengt hWid thPore length
Bri dge angle

122

1.44

0.23

1.58
1.04

62

2.94
2.34
1.47
55

1.97

0.65
20

34.29

0. 18
0.1 5
7.%

Le ngth
W idthPo re length
Bridge angle

62
43
43
43

2.94
2.42
1.2
13

3.82
3. 16
1.92
33

3.45
2.88
1.68
21.5

Le ngthWidth
Pore l ength
Bridge angle

81
71
71
71

3.94
3.25
1.74
45

5.91

81

4.99
4.27
2.46
64.27

0.35
7 .82

Length
Width

223

4.75
4.93

12.84
7 .9 1

9.13
5.95

0.73

Length
Width

484

3.88
2.75

8.42
6.28

5.87
4.1 5

0.7
0 .58

Diameter
Central area
Pore size
No. of elements

452
263
357
99

2.91

5.99
3.57
2.83
33

4.42
2.58
1.70
28

0.49
0.29
0 .25
2.7 1

Diameter
Central area
Pore size
No. of elemen ts

118
95
99

4.43

6.97
3.3
2.18
35

5.93
2.61
!.54
32

0.44

C. leptoporus

E. huxleyi

G.muellerae

G. oceanica

H. carteri
S. pulchra
U. sibogae
var.foliosa

U. sibogae
var. Jibogae

173

5 12

62
62

100

282

50

l.l8

1.77
1.02
17

1.59
0.81
22

2.2 1

5.15

3.34

Mean
7.2 1
22
l.32

Standard
Deviation
1.27
3.89

0.34

0.24
0.2 1

0.2
6.01
0.5
0.47

1.44

0.30
0.29
2.38

Table 1: Statistics showing the morph ological variability of theselected coccolith species at CI6m. Note that in a first phase of thestudy only measurements of lengths/diameters were made, resulting
in diffe rent counts per parameter.

elements is obvious, whereas the diameter of the central
area is less clearly correlated to the coccolith diameter(Figure2).
In total, our data confirm several previous observationsof C. leptoporus morphology (e.g. Mclntyre & Be, 1967;
Bartolini , 1970; Baumann, 1990 ; Kleijne, 1993 ;Knappertsbusch et al., 1997). In particular, the clusteringof the coccolith measurements into three different
morphotypes with minimum overlap at 5Jlm and 8Jlm byKnappertsbusch eta/. (1997) and by Kleijne (1993) is very
similar to our findings. The authors have not found goodcorrelation between these morphotypes and single
environmental parameters. Nevertheless, Knappertsbusch
et al. ( 1997) also showed that individual assemblage plots
might differ significantly from different regions, with either
large, intermediate or small coccoliths dominating. Thus,
the strong dominance in freque ncy ,of the intermediatemorphotypes in samples of CI6m is not surprising.
Conspicuous differences of the morphotypes occur inthe inner part of the shield, especially in the filling of thecentral area. We have found that in the small- and mediumsized placoliths (types A and C, respectively, of Kleijne(1993)), the radial elements extend inward into the central
pore. In contrast, the central area is filled with a ring-likesolid structure, without visible sutures, leaving only a small
central pore in the large-sized morphotype (type B ofK.leijne(1993)). In addition, variation in suture shape has also to
be included in distinguishing between the different
morphotypes (Kleijne, 1993).

Journal of Nannoplankton Research, 22, 3, 2000 .

Emiliania huxley i (Lohmann, 1902) Hay & Mohler, 1967
in Hay et al., 1967 fonns spherical coccospheres consistingof <10 to upto >50 partially interlocked placoliths. Theseoval placoliths typically are formed ofT-shaped elements
and have an elliptical central area. Young & Westbroek(1991) distinguished between different varieties of E.
huxleyi (types A, B, C, and var. corona), ~lthough theystated that biometrical analyses do not separate thesetypes easily. E. huxleyi in general is the most abundant
living coccolithophore and has extremely broad ecologicalaffinities, occurring in all of the main oceanic conditions.
Large-scale blooms which mainly consist ofE. huxleyi areregularly observed during early summer in the northern
North Atlantic (e.g. Holligan et al., 1993; Brown & Yoder,1994). This species is easy to maintain in culture and has
been subjected to intensive studies, combining
observations from culture and oceanic populations (e.g.
Watabe & Wilbur, 1966; Westbroek et al., 1989; Young &Westbroek, 1991; Westbroek et al. , 1993 ; Young, 1994).
The morphology of a total of803 individual coccolithsof E. huxleyi shows a clear unimodal distribution with amaximum centred at 3. 3 J.Ull (Figure 3). Overall, distal shieldlengths are 2.4 to 4.4J.UU, the widths are 2.0 to 3.6f.Ull, andthe number ofT-shaped elements range between 22 and 40(Table 1). Length and width of the distal shield are extremely
well correlated (r'l = 0.93) and a good correlation also exists
between the length of the distal shield and both numbersof radial elements and size ofthe central area (r'l = 0.68 andr2 = 0.548, respectively). Varieties as given by Young &Westbroek (1991) have not been distinguished here.
However, since most of the coccoliths had a grill of curved
rods in the central area (see SEM picture in Figure 3), themajority of the measured specimens are probably type A
coccoliths. A few specimens, with delicate rays and open
(dissolved?) central areas or with remains of a tiny plate,indicate that forms of E. huxleyi type C also occur.
Despite an increasing base ofknowledge onE. huxleyi,
we still know little about its variability in coccolithmorphology. The types of variation observed in the present
study indicate that genotypic variation, as has been
described by Young & Westbroek (1991) for E. huxleyi as
a whole, is not obvious. The population in tllis area seems
to be morphologically relatively homogeneous, a findingthat has been made for other regions as well, especially in
the North Atlantic (Young, 1994). Thus, there might only
have been one genotype present in this area.
Florisphaera profunda Okada & Honjo, 1973 forms
subspherical coccospheres with overlapping, flatcoccoliths (nannoliths), forming a rosette when looking in
top-view. Each single nannolith is a polygonal plate
without any ornamentation. Generally, two varieties ofF
profunda (var. profunda and var. elongata) could be
distinguished (Okada & Honjo, 1973; Okada & Mclntyre,1977). Together with a few other species, it is the main
contributor to the so-called deep-water assemblage (----60
to~ 180m water-depth) oflow- to mid-latitudes (Okada &Honjo, 1973 ; Nishida, 1979; Reid, 1980). In sedimentassemblages, this species has often been overlooked.
However, recently F profunda has gained increasing
attention , since it was shown to be a useful187

Journal of N annoplankton Research, 22, 3, 2000.

K-H.Baumann, C. Sprengel: Mmphological variations of coccolith species... , p. 185-193.

Emiliania huxleyi
3

2

4

._

.. •..

r2 = 0 .931

/

E' 3
.3
.r=

-6

~ 2

,.. ...

"

0

Di stal . hicld
clement'' =;,~/

;: 40
V)

Q)

0

E
Q)

0

Ui 30
'--

0

0

, ..o

0
z 20
2

3
Leng th (J.tm)

2

4

3

4

Length (J.lm)

Frequency

Figure 3 : Co ccolith size variation data and frequency distributi ons (at 0.25filll intervals) of various
parameters measured in E. huxleyi. Measured parameters are indic ated in the SEM picture of thi s
species (representing a type A variety).

palaeoproductivity indicator (e.g. Molfino & Mclntyre,
1990; Ahagon eta!., 1993 ; Bassinotet al. , 1997; Okada&Matsuoka, 1996). The nutrient availability is controlled by
the depth of the nutricline, which can be monitored by theabundance ofF profunda (Molfino & Mclntyre, 1990).
The length and width of the nannoliths are easily
measurable morphometrical parameters in F profunda.
Therefore, and due to the high relative abundance insettling assemblages of the Canary Islands, 496 specimens
were measured in the present study. The distribution showsa unimodal pattern with a maximum centred at about 2.811ffi(Figure 4). Overall, coccolith lengths are 1.6 to 5.91-lm, themaximum widths are 0. 9 to 4.0 llffi (Table 1). Obviously, there
is a great variability in the scatterplot (Figure 4), especiallyof coccoliths >3.51-lm in length. Thus, a rather low
correlation exists between the length and the width of the
2

3

4

5

75

u..e

25

Their increased value as a proxy for nutrients could
possibly advance to a study of the morphological diversityof the whole population.
All extant species of the genus Gephyrocapsa
Kamptner, 1943 build spherical coccospheres of oval
placoliths with a bridge crossing the central area. The
number of extant species within the genus is still a point of
debate and, besides, has often been confused due todifferent taxonomic concepts. This is rather surprising,since Breheret (1978) and Samtleben ( 1980) have alreadydemonstrated that Gephyrocapsa species could relatively
easily be distinguished by a combination of morphologicalparameters, such as the placolith length and bridge-angle.
Recently, morphological analysis of Holocene
Gephyro capsa assemblages revealed six dominantmorphological associations (Bollmann, 1997), which the6n :496>.
u

Florisphaera profunda~ 50
0 ....l.-...u.l.........=..!. :z:t:~:a...-~--...J
4 ,-----------~-------,

2

3

4

5

coccoliths, resulting in acorrelation coefficient of only
r2 = 0.269. Possibly, this isdue to the fact that bothvarieties of F profunda arepresent in the investigatedsamples, with var. e/ongata
forming larger coccoliths (e.g.
Reid, 1980) .
The presented results ofthe study of morphologicalvariation in F profunda arerather preliminary, but give afirst impression of the sizevariability of this species. A
wide range in size of thenannoliths has already been
described and has lead to thesubdivision of this species(Oka da & Honjo, 1973).
However, from the presented
data, this subdivision seems
a little questionable, although
we have not measured thevariation on coccospheres.

6

Length (J.lm)
Figure 4 : Coccolith size variation data of a ll measured F profu nda .

188

author described informally, since he reserved
judgement on whether these corresponded todiscrete species or at least in part toecophenotypes.
For this study, our aims were to test whether
the three species of Gephy rocapsa (G. ericsonii
Mclntyre&Be, 1967, G muel/erae Breheret, 1978,
G. oceanica Ka mptner, 1943), which weredistinguished by Sprengel et al. (2000) in theinvestigated samples, could be separated bymorphological measurements. We measured thelengths of 264 specimens and the width, bridgeangle and central-area size of 136 of these. Overall,
lengths and widths of the placoliths are extremely
well correlated (~ = 0. 995) and a trirnodal distnbution
pattern can be observed in the length data (Figure5). A bivariate plot oflength vs. bridge-angle clearly

K-H.Baumann, C. Sprengel: Morphological variations of coccolith species..., p. 185-193.

Journal of Nannoplankton Research, 22, 3, 2000.

Gephyrocapsa pp.
60
>,

u

c

40

<.)

:::l

o~

20

u.

0
5

E' 4
2:

..c

3

~

2

-o

.-..

E' 3

~

2:

bO 60

..c

c

Oo
c 2
~

0
Cl.

"'00 40
:g 20
<.)

~

0

~
2

Ill
I

I

3

4

6

(

•

,~~·:;t~·0,8 ,,,
'0 ~~
tf"f

0

2

•

e>Ct.l1> c. muellerae

005

G. ocf'tmica (

80

<.)

3

4

5

6

Le ng th (!Jm)

Le ngth (!Jm)

Figure S: Coccolith size variation data and frequen y distributions (at 0.2fun intervals) ofvarious parameters measured in Gephyrocapsa spp. Measured parameters are indicated in
the SEM picture (representing a G. oceanica).

seperates the three modes into discrete clusters. Theseclusters correspond to the above-mentioned species. G
ericsonii coccoliths are 1.4 to 2.91J.m long, ~2 . 31J.m wide,and have medium-large bridge-angles of about 20-55°(Table 1). G muellerae coccoliths are medium-sized, 2.9 to3.81J.illlong and have a typical small bridge-angle of13-33°,
whereas large-sized G oceanica are 3 .91J.ID to 5.91J.ffilong
and have a large bridge-angle, generally >50° (Figure 5).
Thus, our measurements exactly fit into the 'traditional'
scatterplot-scheme of bridge-angle vs. length presented
by Samtleben (1980). In addition, although difficult tocombine, the observed species could be identical tomorphotype associations GM, GC and GE/GL as introduced
by Bollmann (1997), with his ecological interpretation fitting
relatively nicely into the observed composition of theGephyrocapsa assemblage.
Helicosphaera carteri (Wallich, 1877) Kamptner, 1954
forms coccospheres with large, elliptical coccoliths(helicoliths), with a helical flange terminated by an
expanded wing. Three varieties of H. carteri (vars carteri,
hyalina and walichii) are conventionally recognised in
the extant calcareous nannoplankton, based on thehelicolith central-area structure (e.g. Young, 1998), although
it is not clear whether this variation is genotypicallycontrolled. Cros et al. (2000) have found combination
coccospheres of H. carteri heterococcoliths with
Syracolithus catilliferus holococcoliths, from which they
infer that the two morphospecies are life-cycle phases of asingle biological species.
The length of the helicolith is the most easily measurable
morphometrical parameter in H. carteri. Therefore, in thepresent study, data is mainly presented as total coccolith

length and width of the coccolith(both including and excluding thewing: Figure 6) measured on a totalof 223 specimens. Most coccoliths
are between 6 .21J.ID and 12.21J.ID in
length and range from 4. 4 to 7. 91J.m
in width. Length and width are
relatively well correlated to eachother (r2 = 0.586). H. carteri seems
to be unimodally distributed withrespect to coccolith length. However,since we have not included thecentral-area structure as amorphological feature in this study,
different intraspecific varieties havepossibly been analysed together.
This might be the case even thougha conspicuous unimodal frequency
distribution was observed.
Nevertheless, results are promising
to intensify study on themorphological variability of thisspecies.
The
coccosphereofSyracosphaera pulchra Lohmann,
1902 is dithecate, and consists of an
endothecallayer of elliptical, basin-

shaped caneoliths and an exothecallayer of dome-shaped
cyrtoliths. The exothecal coccoliths have a very low
preservation potential so that we have only measured theendothecal coccoliths. Combination coccospheres occur
with both the holococcolithophorids Calyptrosphaera
oblonga and Daktylethra pirus . These combination
coccospheres can have various possible causes. Cros etal. (2000) argued that this might indicate a particularlycomplex life-cycle. However, the association of two
holococcoliths, which do not occur on the same cell, with
one hetero-coccolithophorid is probably due to cryptic
speciation inS. pulchra morphology (Geisen et al., 2000).
In our study, we have measured only length and widthof the endothecal caneoliths. The measurements on a totalof 484 caneoliths show a clear unimodal distribution pattern(Figure 7). In general, the population was consistently
characterised by medium-sized coccoliths, most of them 571J.m long and 3.5-51J.m wide. Overall, the length of tl1e
caneoliths ranges from 3. 91J.ID to 8. 41J.m, and the width from
2.7 to 6.31J.ffi (Table 1). The lengths and widths are strongl2
correlated to each other, with a correlation coefficient of r
=0.846 (Figure7).
Detailed morphological data on S. pulchra does not,to our knowledge, exist so far, although it is the most robust
Syracosphaera species and is characteristic of temperate
to subtropical coccolithophore assemblages (Jordan &Chamberlain, 1997). Therefore, the present study gives afirst basis for the morphometrical characterisation of thisspecies.
Umbilicosphaera sibogae Weber-van Bosse, 1901
forms non-motile, spherical coccospheres covered withcircular placoliths. It contains two varieties, most probably

189

Journal of Nannoplankton Research, 22, 3, 2000.

;>,

Helicosphaera carterin = 22340

K-HBaumann, C. Sprengel: Morphological variations of coccolith species..., p. 185-193.

(.)

~
5- 20
!::?
u.
0
8

r2 = 0. 5

E' 7

3
.c 6
-6

3

0

o oo~·'
0~~ill ""h
0

~0

5

~'f,

0

·'

4
4

?~o

6

_,.· '·'

0

8

,,

10

8

12

14

Length (J.Jm)
Figure 6 : Scatter plots and frequency di stribution (at 0.25J.1m intervals) of all H. carteri
coccoliths measured. ote that the specimen shown in the SEM picture has an unusually wide
wing.

Syracosphaera pulchra
4

5

6

7

8

9

100
n =4 4

;>,
(.)

c

<!.)

g_ 50
<!.)
.....

u.

0
7

6

E' 5
3

-5

"0

4

3 3
2
4

5

I

I

I

6

7

8

Lenglh (J.lm)

9020 40 60

Frequency

Figure 7: Scatter plots and frequ ency distributi on (a t 0.2J.Im interva ls for the cocco lith
length; at 0 .25J.1m intervals for the coccolith width) of all S. pulchra coccoliths measured.

discrete genotypes, showing distinct variation incoccosphere form : U. sibogae var. sibogae (Weber-van
Bosse, 190 1) Gaarder, 1970 forms a large coccosphere with
about 40-100 partly interlocked, circular placoliths, whichhave a relatively large central opening. Proximal shields
usually are larger, or as large, as distal shields. The
coccosphere of U. sibogae var.fo/iosa (Kamptner, 1963)
Okada & Mclntyre, 1977 is smaller in diameter and consistsof <30 tightly interlocked, circular coccoliths with arelatively small central opening, and with proximal shields
smaller than distal shields. Detailed descriptions of thecoccolith morphology are given in Okada & Mclntyre ( 1977)
andKleijne (1993).
In our study of 569 individual coccoliths, the twovarieties show distinct variation in coccolith diameter,
element numbers, and size, both of the central area and thepore (Figure 8). The distal shield of U. sibogae var. sibogae

is 2.9J.UU to 6.0J.lffi in diameter andconsists of21(17)-33 elements (Table1). Proximal shields are larger than the
distal shields, but have not beenmeasured in our study. The distal
shield of U. sibogae var-. foliosa is
4.4f.1m to 7.0f.1m in diameter, andconsists of26(22)-35 elements. The
distribution of each of the varieties is
unimodal with peaks centred at 4.4f.lill(var. sibogae) and, less clear, at about
5.9J.UU (var.jo/iosa), respectively. A
good correlation of most of theparameters (pore size, diameter of thecentral-area, number of distal shieldelements) exist with the diameter ofthe distal shield, with correlation
coefficients ranging between~= 0.49
and~= 0.667 (Figure 8). The absolute
range, both of the pore-~ize and of
the central opening, is very similar forboth varieties, indicating that therelative proportions with the diameterof the distal shield are smaller for var.
sibogae.
In general, our findings very well
fit to previously publishedmorphological data on U. sibogae(e.g. Okada&Mclntyre, 1977;Kleijne,
1993). Although the morphology ofboth varieties slightly overlaps,
identification usually was never a
problem in our samples.

Seasonal variation of morphological associations:
The investigated coccolith species
show surprisingly little morphologicalvariation throughout the year,
although strong seasonal coccolith
fluxes, coinciding with variation in

SST, are well illustrated at ESTOC from November 1995 toNovember 1996 (Sprengel et al., 2000; Figure 9). In
particular, this is the case for the variation in mean lengthof E. huxleyi, which is about 3. 3 J.lffi throughout the year.
The frequency distribution of the single samples, however,display less clear (unimodal) distribution tl1an that of thetotal population (Figure 3). This is probably an artefact of
the lower number of measurements in comparison to thetotal population. However, the maximum range in size ofE.
huxleyi generally exhibits a pulsating pattern of minor
variation during bloom phase, and slightly wider
distribution of lengths in pre- and post-bloom samples.
Conspicuous variation in size-distribution between single
samples of the sediment trap can also be seen in most of
the other species, especially in F profunda, without
revealing any seasonal pattern. This is in contrast to
seasonal trends in species occurrences, with highest

190

K-H.Baumann, C. Sprengel: Morphological variations of coccolith species ... , p. 185-193.

Journal of Nannoplankton Research, 22, 3, 2000.

Umbilicosphaera sibogae
Di tal sh ield element

>-

u
c:
~ 50
0'

~

lL.

t::::
;·

"'0

0

'E

a 3

3

3
~ 2

~

!!?.

•

v:tr. 'i/loww
r2 = 0.52

..,

('I)

('>

-~

~

0

area

Q..

40

\'ar . .,·ibogo~.~Vlc:, 2 = 0.552

<!)

E
<!)

30

U5
.._
0

var.foliosa
r2 =0.667

2

3

4

5

6

Diameter (IJm)

7

••

0
z 20

8 0

30

•

60

2

Frequency

3

4

5

7

6

8

Diameter (1Jm)

Figure 8: Scatter plots and frequen cy distribution (at 0.2f!m interva ls for the coccolith diam eter; at O. lf!mintervals for the central area) of all U. sibogae coccoliths measured. Measured parameters are indicated in the
SEM picture (representing U. sibogae var. sibogae) .

relative abundances of the deep-dwelling F profimda inpre- and post-bloom phase and clearly dominating E.
huxleyi during bloom-phase (Sprengel et al., 2000). U.
sibogae also shows only little variation iP placolithmorphology with increasing total coccolith flux anddecreasing temperatures. However, only results of U.
sibogae var. sibogae are shown here due to the fact that
increased numbers of var. foliosa only occur in 'bloom'
samples, whereas this variety is very sparsely present in
the pre- and post-bloom samples. This finding corresponds
well with the observations ofBroerse et al. (2000), whoshowed that var. foliosa becomes more abundant in
nutrient-enriched (upwelling) regions, whereas var. sibogae
is thought to be associated with oligotrophic conditions.
Nevertheless, very slight morphological variations of bothvarieties are less than the standard deviation (Table 1) anddo not display any seasonal trend.
The only noteworthy exceptions seem to be the size
variations in C leptoporus. However, although the absolute
variation in the diameter ofC leptoporus is l.51Jfll (6.681Jill
to 8.l8Jllll), which is 20%ofthesize, a clear seasonal pattern
is not revealed (Figure 9). Highest and lowest mean
diameters are found in winter samples (November/
December 1995 and December 1996, respectively). Whether
this is due to the low number of measurements in some ofthe samples or to a real trend remains rather unclear.
However, as shown before, three different morphotypesof C leptoporus occur, and their appearance may beenvironmentally controlled (Knappertsbusch et al. , 1997).
In total, the results of this study suggest that oceanic
populations from distinct regions, such as the CanaryIslands, are relatively homogeneous with respect tococcolith morphology, probably representing only part of

the total genotypic
heterogeneity of theinvestigated species.
Thus, the total
variation in coccolithmorphology of a
distinct species canonly be identified ona global distribution.
Different
morphotypes of a
species, however, may
have
distinct
ecological
adaptations, as isindicated by bothvarieties of U.
sibogae. In fact, there
is increasing evidence
that morphologicalvarieties
reflect
genotypicratherthan
ecophenotypicvariation (e.g. Young& Westbroek, 1991;
Knappertsbusch etal., 1997; J. Young,pers. comm., 2000), of which the distributions areenvironmentally controlled.
Conclusions
In summary, all investigated coccolith species generally
are characterised by a relatively strong correlation of thevarious parameters measured. They all exhibit a unimodal
distribution of lengths/diameters and show only slightmorphological variation throughout the year. This is rather
surprising, since strong seasonal coccolith fluxes,
coinciding with variation in SST, are well illustrated at thetrap position north of Gran Canaria. Thus, it is suggested
that these populations represent a local part of the total
genotypic morphovariability of the species.
Acknowledgements
We are grateful to M. Geisen and J.R. Young, who madevaluable suggestions on the manuscript. This research
was originally funded by the MAST Ill program, CANIGO(Canary Islands Azores Gibraltar Observation), subproject'Particle flux and palaeoceanography in the Eastern
Boundary Current System', and has later constituted partof the EU-funded TMR Network Project, CODENET(Coccolithophorid Evolutionary Biodiversity and Ecology
Network).

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